An international counterterrorism conference has begun in Sri Lanka, amid military reports of more violent clashes with rebels in the island's north.

Sri Lanka's foreign minister Rohitha Bogollagama opened the three-day conference Thursday in the nation's capital of Colombo, saying the international community must work together to combat terror networks.

Meanwhile, military officials said Thursday at least 34 Tamil Tiger rebels have been killed so far in fighting that began Wednesday near the northern town of Omanthai. The town serves as the defacto border separating government and rebel-held areas.

In a separate incident Thursday, Sri Lankan officials say at least four people were killed in a sea battle off the northwest coast of Mannar district.

The military says navy boats intercepted suspected rebel boats, and fighting erupted. The navy later recovered a boat with four bodies, and at least three survivors. Officials do not know if the dead are rebels or civilians.

A pro-rebel Web site claims the boat was carrying civilians who were fleeing Sri Lanka for India.

Tamil Tiger rebels had no comment on the clashes, and no independent confirmation of the military's claim was immediately available.

Minority ethnic Tamils have been fighting for an independent state in Sri Lanka's north and east since 1983. Nearly 70,000 people have died in the fighting, including 5,000 people killed since a cease-fire pact broke down last year.